1. Field of the Invention
The present invention generally relates to a printed circuit board and a method of manufacturing a printed circuit board for a semiconductor package. More particularly, the present invention relates to a printed circuit board having a structure that can prevent the generation of cracks around a window slit when the window slit is formed in a base substrate.
2. Description of the Related Art
Semiconductor packages having a board on chip (BOC) structure are being used more frequently as the operation speed of memory semiconductors increases. In the BOC structure, a semiconductor chip is directly mounted on a printed circuit board whereas in conventional semiconductor packages electrical signals are transmitted between an integrated circuit (IC) and a circuit on substrate through a lead frame of a packaged semiconductor. The BOC structure has an advantage in that thermal and electrical problems caused by the high speed of a DRAM of semiconductor devices can be effectively handled.
FIG. 1 is a cross-sectional view illustrating an example semiconductor package having a BOC structure. The BOC structure package uses a printed circuit board 10 having a window slit 15 formed in the center thereof. A semiconductor chip 20 is bonded on an upper surface of the printed circuit board 10 using an adhesive 30. The chip 20 is configured on the board 10 such that an electrode unit 23 of the chip 20 is oriented in an inner space of the window slit 15 of the printed circuit board 10.
The printed circuit board 10 includes a base substrate 11, a circuit pattern 12 formed at least on a side of the base substrate 11, and a protective layer 13 that protects the circuit pattern 12. A conductive ball 14 that is configured for electrical connection to an external substrate (not shown) is formed in a void or gap of the protective layer 13 such that the ball 14 contacts the circuit pattern 12.
In this case, the electrode unit 23 of the semiconductor chip and the circuit pattern 12 of the printed circuit board 10 are electrically connected by a wire 33. Thus, the wire 33 passes through the window slit 15. A region where the wire 33, the electrode unit 23, and the circuit pattern 12 are included may be molded by a molding material 40 to protect the wire 33 from being damaged or accidentally disconnected.
The printed circuit board 10 for the BOC may be manufactured in the form of a strip, sheet or tape. The printed circuit board 10 may be formed by sintering a resin pressed by a glass fiber matrix. Usually, the window slit 15 is formed in the printed circuit board 10 by using a drill, for example after stacking a plurality of sheet shaped printed circuit boards.
In this case, to accurately set the position of the window slit 15, a hole having a predetermined size is first formed through a laser processing. Afterward, the window slit 15 is formed using a drill. Accordingly, formation of the window slit 15 is a two step process that thereby increases manufacturing time and costs.
Recently, the printed circuit board 10 can be formed more efficiently by a reel-to-reel (roll-to-roll) process. However, when a drill is used to form the window slit 15, the manufacturing time is further increased.
To reduce the hole forming time and manufacturing costs, a punching process can be used. However, when pressure is applied to the printed circuit board 10 to perforate the window slit 15, cracks can be generated at the cutting surface since the printed circuit board 10 includes glass fiber. The cracks can degrade the appearance of the printed circuit board 10 and affect circuit patterns.